1. Field
The disclosure relates to communications circuitry, and in particular, to a receiver front end featuring jammer resistance and noise cancellation.
2. Background
In designing communications receivers, it is generally desirable to provide a low-noise front-end to overcome noise contributions from subsequent stages of a receive chain. Certain prior art implementations employ a noise cancelling architecture for the receiver front end, wherein signal currents generated by two signal paths are weighted and summed together to cancel noise.
Several considerations arise in the design of such noise cancelling receivers. In particular, additional filtering can be provided in the receiver to achieve adequate rejection of out-of-band interferers (or jammers). However, such additional filtering usually results in higher insertion loss. The receiver may also be designed for better linearity, though generally at the cost of higher power consumption and/or higher noise.
In some implementations, to perform baseband combining of signal currents from the two signal paths, the receiver may be provided with additional trans-impedance amplifiers or baseband combiners at the back end. Alternatively, resistor strings may be used to perform the summation. However, these approaches suffer from various drawbacks, e.g., higher power consumption in the case of additional amplifiers and/or combiners, or limited signal headroom in the case of resistor strings due to DC (direct-current) IR (current-resistance) drops.
It would thus be desirable to provide techniques for designing a noise cancelling receiver front end that provides significant out-of-band interferer rejection, while further consuming less power than existing prior art implementations.